A San Francisco-connected Web developer and his architect sister survived a harrowing ordeal in the Caribbean Sea after their small fishing boat sank 8 miles offshore, leaving them to swim for their lives, authorities said.

Dan Suski, 30, and Kate Suski, 39, had left the island of St. Lucia on Sunday morning on a chartered 31-foot fishing boat called the Reel Irie, officials said.

Around 12:30 p.m., the boat suddenly began taking on water, according to St. Lucia Marine Police Sgt. Finley Leonce. The shaky weather didn't help, and the weather service had warned small boats to stay near shore that day.

"We're not exactly sure where or how the water was entering, but the volume of water was more than the watering system could handle," Leonce said.

The boat's captain, 37-year-old Griffith Joseph, and first mate Timothy Cooper, 28, managed to radio out a distress call giving the location of the boat, but it soon became clear the Reel Irie was going down, officials said.

All four people on the boat jumped out with only life vests to keep them afloat. The boat dropped under the water's surface, and waves pushed Joseph and Cooper away from the Suskis. The siblings at first waited for rescue, but as hours passed and the sun set they reportedly decided they couldn't stay still.

Marine police responding to the distress call hit the water to search for the couple and crew, assisted by a plane and a helicopter from a rescue center in nearby Martinique. Private vessels helped with the search, Leonce said.

They hunted until late into the evening, but found nothing, Leonce said. In the morning, they resumed the search - and then, around 7 a.m., search crews got an unexpected call.

The Suskis were alive - dehydrated and weak, with their necks severely scratched from the life vests- but alive and wandering on St. Lucia's Dauphne Beach.

They had swum for 12 to 14 hours, fighting off fears of sharks, leg cramps and hypothermia before pulling themselves onto the sand in the wee hours of the next morning and sleeping a short while, they told the AP. After reviving a bit by eating wild mangoes and green bananas, they found an island worker who called authorities - who rushed over with ambulances to take them to the hospital, Leonce said.

Leonce said it was his understanding that Dan Suski was either from or connected to San Francisco. His sister is apparently an architect in Seattle.

Meanwhile, the search for Joseph and Cooper stretched for nearly 24 hours until around 11 a.m., when the crew of a fishing boat helping with the search rescued them, Leonce said.

"They were spotted on the water, waving their arms to attract the vessel captain," Leonce said. "They were still very strong, still swimming toward shore."